function [ DrI ] = getDrI( r, rn, I )
%GETDRI Summary of this function goes here
%   Detailed explanation goes here

down = (r(1)^2+r(2)^2);

s = 3 * log(rn);
A = I;
ds = 3 * [r(1), r(2)] / down;
dA2 = [0,0,0,0;0,0,0,0];
dA = reshape(dA2, 2, 2, 2);

DrI = tensorProductGradient(s, ds, A, dA);

end

